1. Field of the Invention
The present invention relates to a filter element including an inductor.
2. Description of the Related Art
Currently, various filter elements are used as high-frequency components for use in communication modules. One of those filter elements is an LC filter element including an inductor and a capacitor.
As disclosed in Japanese Unexamined Patent Application Publication No. 11-97963, for example, the above-mentioned type of filter element is configured using a laminate in which an inductor and a capacitor are defined by internal conductors.
The LC filter element disclosed in Japanese Unexamined Patent Application Publication No. 11-97963 includes two parallel resonators each including an inductor and a capacitor. Respective inductors of the parallel resonators are magnetically coupled with each other through a mutual inductance. A desired filter characteristic is achieved by utilizing the magnetic coupling.
To obtain the above-mentioned magnetic coupling, in Japanese Unexamined Patent Application Publication No. 11-97963, linear conductor patterns for the respective inductors of the parallel resonators are formed in different layers of the laminate. Furthermore, the linear conductor patterns for the inductors are arranged in an overlapping relationship when viewed in the laminating direction of the laminate, while an insulator layer having a properly adjusted thickness and arranged to adjust the mutual inductance is interposed between the linear conductor patterns.
However, with the arrangement disclosed in Japanese Unexamined Patent Application Publication No. 11-97963, because the desired magnetic coupling is obtained by changing the thickness of the insulator layer for the adjustment of the mutual inductance, an achievable range of the magnetic coupling (i.e., an available range of the mutual inductance) is restricted by dimensional limitations of the laminate. This causes a problem, for example, in that the desired filter characteristic may not be obtained depending on the dimensions of the laminate. Moreover, a degree of flexibility in design of the filter characteristic is reduced.